-> 2 seconds delay in calls,

-> Dial tones very loud (despite developers assurances for a future version, which is published by now, it's not possible to lower the dial tones volume separately from the main volume),

-> at every startup Apples firewall comes up again (not as with other applications) and if you don't allow incoming connections fast enough you won't hear the receiver of your call,

-> every(!) call breaks up after about 35 to 36 minutes,

-> and the developers mostly don't reply to eMails.

These are all quite annoying flaws. Makes the programme look like some kind of hobby project, except for the price.